Steering Column Resilient Contact Device
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Solution Overview
Problem
The existing collapsible steering column assemblies experience free play between the telescopic shafts due to manufacturing tolerances, leading to potential vibration and rattle noise issues, which are not adequately addressed by existing spline-based designs.
Innovation Solution
A contact device with a resilient contact member is introduced at the end of the second shaft, secured by a fastener, to take up radial free play between the shafts, ensuring precise alignment and reducing vibration by modifying the natural frequency of the shafts. The resilient contact member, often conical or petal-shaped, is designed to apply a controlled static force to the splines, preventing relative rotation and enhancing stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dimensional tolerances are controlled tightly to eliminate free play between shafts, then manufacturing precision improves, but manufacturing complexity and cost increase significantly
Solution Approach 1:
A resilient contact member is introduced as an intermediary element between the first and second shafts. This member actively compensates for dimensional tolerances and eliminates free play without requiring tight manufacturing tolerances on the shafts themselves, thereby resolving the contradiction between manufacturing precision and device complexity
2Strength
If the resilient contact member applies greater static force to the splines, then stiffness and vibration reduction improve, but friction between splines increases causing binding
Solution Approach 1:
The resilient contact member is designed with specific material properties and geometric parameters (such as durometer hardness and contact surface area) that allow it to apply optimal static force to the splines. This enables sufficient stiffness and vibration reduction while maintaining low enough friction to prevent binding during telescopic movement
3Reliability
If the steering shaft is designed to collapse telescopically for crash safety, then crash safety improves, but free play between shaft portions increases
Solution Approach 1:
The resilient contact member serves as a mediator that eliminates free play between the telescopic shaft portions while preserving their ability to collapse relative to each other during a crash. This resolves the contradiction by providing active compensation for gaps without constraining the crash collapse function
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces vibration-induced rattle and improves the stiffness of the steering column assembly by eliminating radial free play, ensuring a stable and quiet operation while maintaining the telescopic functionality for crash scenarios.
Implementation Method 1
a resilient contact member that contacts the tips of a plurality of the splines of the first shaft, thereby to take up any radial free play between the end of the second shaft and the first shaft
Implementation Method 2
modifying the natural frequency of the shafts. This may also help prevent a rattle noise being produced from the steering shaft
Data Source
Figure 1
Figure 2~3(b)
Figure 4
AI summary
A collapsible steering column assembly (100) comprises a telescopic steering shaft that is supported within a steering column shroud, comprising a first shaft (103) having a hollow end, the inner surface of the hollow end being provided with a plurality of inwardly facing elongate splines (103A) that each extend axially along the inner surface, and a second shaft (104) that has an end that is located within the hollow end of the first shaft (103), the second shaft (104) being provided with a set of outwardly facing elongate splines (104A) that each extend axially along the outer surface of the end of the second shaft (104), the splines (104A) of the second shaft (104) inter- engaging the splines (103A) of the first shaft (103) to prevent relative rotational movement of the two shafts whilst permitting the two shafts to move axially relative to one another at least in the event of a crash. A contact device is located at the end of the second shaft (104) that is located within the hollow end of the first shaft (103) that includes a contact member (108) defining a contact part that contacts the tips of a plurality of the splines (103A) of the first portion, thereby to take up any radial free play between the end of the second portion and the first portion at least in the location of the contact device.